Potentiometers



Sept 24, 1963 R. L. FERRELL T-AL 3,105,217A

PoTENTIoMETERs Filed March i507,r 1962 2 Sheets-Sheet 1 INVENTOR: 2055?? fen BM 5a@ Z #p20/50W Sept 24, 1963 n.1.; FERRELL ETAL 3,105,217

PoTENTIoMETERs Filed March so, 1962 2 sheets-sheet 2 United States Patent O 3,105,217 ETENTMETERS Robert L. Ferrell and Wiibur T. Hardison, Riverside, Calif., assignors to liourns, lne., a corporation Fiied Mar. Sil, 1952, Ser. No. 183,855 i9 Claims. (Si. 338-174) This invention pertains to potentiometers, and more particularly to improvements in potentiometers wherein adjustments are effected by rotation of a screw-threaded worm or Wormscrew. Examples of potentiometers of the general class to which the invention is directed are illustrated in U.S. Patents Nos. 2,945,198; 2,887,554; and 2,880,293. Such potentiometers comprise an elongate arcuate resistance element disposed around the axis of a rotary contact device that is rotated either directly or through clutch means by a worm wheel that is in turn operated by the adjusting wormscrew.

Potentiometers of the class here of interest include cases or'housings of generally square plan-form, or of square shape with one corner beveled for convenience in using ilexible-lead terminals; and in general are constructed to utilize an outer or rim portion of the housing for accommodation of mounting-devices such as screws or bolts. ln some such instruments a set of throughbores or holes is provided for mounting screws, and in other such instruments a set of indentations around the periphery is provided for reception of wires or other fastening elements. As a consequence of those characteristics, the interior space allotted to the resistance element is restricted so that a resistance element of only relatively small radius can be used. Further, only substantially identical instruments (that is, those with matching mount- `ing holes or grooves and of the same over-all dimensions), can be stacked and mounted in face-to-back relationship.

Additionally it may be noted that in the known priorart worm-gear adjusted potentiometers certain compromises were necessary to avoid stripping of the teeth of the wormwheel in the event the wormscrew was overrun, that is, rotated beyond prescribed limits. Thus such a potentiometer might on the one hand have a rotary contact that was permitted to be rotated through an indefinite number of revolutions in either direction, that is, no stop means were provided. in that type of device the potential division drops suddenly from a maximum to a minimum or open circuit Zero value (or vice versa) incident to continued wormscrew rotation. Such operation, or the possibility of such operation, is inmany circuits extremely undesirable. Hence in other prior-art wormscrew-adjusted potentiometers certain stop or movement-restricting means are employed to positively preclude rotation of the rotary contact through a complete revolution. Since the interior mechanism of such potentiometers is not visible to the operator of the device, continued wormscrew rotation during an adjusting operation brings into action the stop means, after which further rotation of the Wormscrew in the same direction must result in damage such as stripping of teeth from the wormwheel, unless slip-clutch means are provided. Thus the alternative choice in the compromise has been to provide such clutch means. Provision of such clutch means, usually in the form of plate-like friction means, presents the possibility of the clutch slipping without effective rotation of the rotary contact, thus nullifying the adjustment effort.

The present invention eliminates mounting holes or grooves at or near the outer periphery of the potentiometer, and utilizes for reception of mounting or fastening means, a single hole that is disposed at the center of the potentiometer and extends therethrough from face n sassari Patented Sept. 24, 1963 to back of the instrument. The single mounting hole is preferably and conveniently produced along and around the axis of rotation of the rotary contact and Wormwheel, and thus is not only located in a region of little value within the instrument and thus permits use of a much longer resistance element, but the hole is also so located and such that potentiometers of various sizes and capacities can be readily and economically disposed or stacked together and secured in place by the same single mounting screw or rod. In providing the mounting hole, the potentiometer housing is so formed that requisite strength is provided, and electrical isolation and protection is provided for the operating components from foreign matter and the mounting screw or rod. Further, by novel means, the present invention provides for positive limitation of rotation of the rotary Contact to a prescribed arc of less than one turn, eliminates the extra means involved in provision of a clutch-device, and concurrently positively avoids possibility of stripping of teeth from a wormwheel. rl`hese results the invention attains by utilizing as a Wormwheel, a bobbin-shaped Wheel having preferably toothless peripheral iianges which press against or grip the thread or screw of the wormscrew and hence cause the wheel to rotate incident to rotation of the wormscrew. The wheel is molded from a resiliently preferably insulative material, with an integral stop, and is formed to engage and directly rotate a conductiveV contact device that brushes on a collector ring and on the arcuate resistance element. Upon continued rotation of the wormscrew following arrestment of contact rotation by engagement of the stop with an abutment provided in the instrument housing, the Wormscrew thread merely slips on the inner surfaces of the flanges. Thus the potentiometer is, functionally, simpler and less complicated and expensive than the prior-art potentiometers having clutch devices, while avoiding the aforementioned undesirable feature of those wormscrew-adjusted potentiometers that do not include clutch means. Additionally, by placing the resistance element adjacent the outer Wall of the potentiometer housing, and providing a heat-receptive and heat-transmitting member at the center of the housing, heat-transfer from the potentiometer is' greatly improved over that presented by the prior art wormscrew-adjusted potentiometers.

The operating parts of the potentiometer, comprising essentially a resistance element, contact means, wormwheel means and wormscrew means, are disposed in a two-part case or housing that is formed preferably of dielectric material and that is preferably produced by molding procedures well known in the art. One housing part, herein called a cover, is provided with a centrally located tubular portion or member Whose interior bore provides the mounting hole for the instrument, and which tubular structure serves to absorb compressive mounting forces and also serves as a shaft upon which a wormscrew-actuated wheel and a rotary electric contact are mounted for rotation. The interior of the housing provides a generally toroidal space in which operating parts are disposed, the resistance element and a collector ring conductor being mounted in or on the base or body part of the housing with terminal means, and the remainder of the operating parts being disposed in the cover part. The two parts of the housing are provided with interiitting portions including outer wall portions through one of which a driving-head portion of the Wormscrew is accessible. The two housing parts, with respective components assembled therein, are arranged and adapted to be secured together by adhesive.l The adhesive, together with seal means provided for the driving end of the wormscrew, permit the interior of the housing to be sealed to prevent ingress of foreign matter. Preferably the housing parts are of square plan form; however, as will be evident, other housing configurations may be used.

The invention provides for restricting rotation of the movable contact to an are somewhat less th-an 3610", that is, less than lone vfull turn; and provides stop means for that purpose which stop means are effective to posi-Y tively preclude rotation of the contact olf either end of the arcuate resistance element. Further, vwithout interposition of clutch means between the worm1'screwdriven wheel and the rotary contact, the invention provides means that permit indefinitely continued rotation of the wormscrew in either direction, without harmful results. To the described ends, the invention provides a toothless Wormscrew-driven wheel positively connected to the rotary contact to drive the latter, the wheel having a pair of opposed stiflly resilient circumferential flanges similar to those .of a pulley and between which flanges a' screw-threaded portion of the wormscrew is gripped to provide a yieldable but driving engagement. The wheel is provided with a protuberance or extension which serves as al stopmember that is rotatable in either direction into engagement with a cooperative stop or abutment provided on one of the housing parts, whereby rotation `of the wheel is positively limi-ted to movement within a predetermined range of rotation. Thus upon continued rot-ation of the wormscrew in either directionl the contact isy drivenv along the'resistance element until Y' the protuberance on'the wheel is arrested by the abutment, after which occurrence the thread of the'wormscrew slips relatively to the flanges otf the wheel. Su-bsequent reverse rotation of thewor'mscrew causes immediate corresponding rotation yof the Wheel in the opposite direction. Thus in effect the wormscrew-and-wheel drive is a positive drive outil and unless the protuberance on the Vwheel enga-ges the stop or abutment, and is in effect a slip-clutch drive when the protuberance is bein-g arrested by the stop or abutment.

The preceding brief general descrip-tion of the invention makes it evident that one prin-cipal object of the invention is to provide improvements in ywormscrewadjusted potentiometers. n f

Another principal object of the invention is to provide simpler and more effective actuating means forV wormscrew-adj-usted potentiometers.

Another principal object of the invention is to provide Vmore effective and versatile 'means for mounting rwormscrew-adjusted potentiometers. Y Y

Another object of the invention isV to provi-de an improved arrangement of parts in'a wormscrew-adjusted potentiometer whereby a resistance element of optimumV length may be used.

Another object of the invention is to provide a wormscrew-adjusted potentiometer `having a simple and inexpensive but very effective wormscrew and wheel arrangement.

An additional object of the invention is to provide for wormscrew-adjusted potentiometers a simple anda effec- V,tive wormscrew-'driven wheel yfor actuating ri'ntlatable driven means of the potentiometer.

Another object is to provide a wormscrew-adjnsted potentiometer having greatly improved heat-dissipation characteristics.

Other objects and advantages of the invention will hereinafter he stated or made evident in the appended 4 components supported by the cover in place, and with portions broken away to delineate details of construction;

VFIGURE 4 is a sectional view of a portion of the potentiometer depicted in FIGURE l, the view being taken as indicated by line 4 4 in FIGURE 3;

' FIGURE 5 is atop view of the base or body part of the housing of the potentiometer depicted in FIGURE l,

illustrating details of the internal configuration of the position;

part;

FIGURE 6 is a top view of the ybase or body part of the housing of the potentiometer depicted in FIGURE 1, Vwith parts supported by the body shown in operating FIGURE 7 isv a sec-tional view of the potentiometer depicted in FIGURE 1,'the section being taken on a plane and in the direction indicated by line 7 7 of FIGURE l;

FIGURE 8 is a face view of 'a wormscrew-drfi-venwheel forming a plural-function component of the potentiometer illustrated in FIGURE l;

iFlGURE 9 is a side View of the component depicted in EIGURE'8;

FIGURE l0 is a kplan view of a worrnscrew comprisedin the potentiometer depicted in FIGURE 1;

' FIGURE ll is a pictorial VView of an electrical collector ring comprised in the potentiometer depicted in FIG- URE'l; l

yFIGURE l2 is a plan View of an insnlator-spacerused in the'potentiometer; l

FIGURE 13 is a bottom view of a resistance'element comprised in the potentiometer depicted in FIGURE l,

With termination tabs applied, the View being taken in a direction indicated by the arrow E in FIGURE 7;

`FIGURE 14 is a plan view of a rotary electrical con- Itact device comprised in the potentiometer depicted in FIGURE l; and

FIGURE l5 is a view in elevation of the device depieted in'FIGURE 14.

Referring rst to FIGURE l', it may be noted that the potentiometer, designated'generally by ordinal 1i?, is of generally rectangular face form, and preferably of square plan form. The operating components of the potentiometery are .enclosed in a housing which preferably comprises two principal members each oi which preferably is formed as a single molded part. As shown, the housing includes a cover partll `and a hase or body part 14, which parts have closelyrinterfitting edge portions which permit the parts to be adhesively or otherwise secured together along a zone of juncture lila and along a juncture or zone of contact ltlb. As will be noted more in detail later herein, the potentiometer includes terminals which in the illustrated exemplary embodiment are in the form of flexible wires or leads and which comprise rality of potentiometers according to the invention, upon vsistance-element terminals 16 and I6'.

a movable-contact terminal l5 and first and second re- Adjustrnent of electrical potential values between terminal 15 and either of the other terminals is effected by rotation of wormscrew means which comprises a driving head lh'that in Y :the exemplary embodiment protrudes vfrom the housing and is thus accessible for operation; As will be described more fully'hereinafter, the cover part l2 has a preferably cylindrical part or portion 12o, the extremity of which vextends through and closely fits ya hole in body part 14 and may be substantially flush with the vsurface of the body part as shown. The tubular interior of the portion 12C provides the hole lith through which a mounting screw or the like may extend, as will presently be made more evident.

`As is indicated in FlGURE 2, several potentiometers according to the invention, and of the same size or of several sizes, may be supported in face-toback relationship on a single common fastening or mounting device. As depicted, three miniature potentiometers P, a small potentiometer Q, and a larger potentiometer R, are all mounted upon a single machine screw S, by which screw and the associated nut N and washer W the potentiings provided by the bore 12b and ometers are secured to one face of a sheet-like panel T. As is evident, the heads of the adjusting wormscrews may all be oriented in the same direction, or otherwise as choicev or conditions may dictate. Equally evident is the fact that potentiometers may be disposed in spacedapart relationship along a common single screw or rod, with spacers, nuts or other clamping means securing the individual potentiometers in their respective positions.

With attention directed to FIGURES 3 and 4, the cover part 12 is preferably formed as an integrally molded member of dielectric material, having a generally rectangular exterior configuration defined by a oor 12f and side walls such as 12W. As previously noted, the cover part comprises a cylindrical part 12e that is centrally located and perpendicular to the floor 12]', and whose tubular interior provides the mounting hole h. Disposed through a suitable bore formed in one wall of part l2 is the wormscrew 18, the inner end 18e of which is disposed for rotation in a groove 12g formed in a buttress provided adjacent one corner of the part. The Wormscrew (FIGURES 3, 4 and l0) is provided with a shoulder 18s upon which is received a sealing O-ring 19 (FIGURE 4), which ring is also received in a step-portion of a properly shaped bore 12b formed in the sidewall of part l2. The wormscrew is retained in position with the indicated bearing surfaces thereof seated in the beargroove 12g, by a retainer pin 20 (FIGURE 3), which retainer pin is received in a well or bore in-cover part l2 as indicated and which is thus disposed in tangential engagement with the wormscrew within a circumferential retainer groove g formed adjacent the head of the wormscrew as shown.

The wormscrew is adapted to engage and induce rotation of a wheel 22 (FIGURES 3, 4, 7 and 9). To that end the wormscrew 18 comprises a worm or thread l8r that is received between and engages portions of the inner faces of opposed resilient `flanges 22], 22]" of wheel 22, as is indicated in FIGURES 3 and 7. The thread 133i is preferably produced of length such that the end portions thereof both engage the inner faces of the anges. Thus as illustrated, the thread does not extend beyond the contines of the groove 22g of wheel 22. Further, to provide an eifective driving interengagement of the thread l8r with the anges of wheel 22, the outside effective diameter of the thread is made slightly greater than the perpendicular distance between the inner faces of the ianges, whereby the flanges are, in the vicinity of the Zone of interengagement, slightly sprung apart and thus caused to lirmly grip the thread. The Wheel 22 is thus preferably made of a suitable tough slightly resilient synthetic resin or polymer, of which a material marketed under the trade name Nylatron GS by The Polymer Corporation of Reading, Pa., is eminently suitable. While herein illustrated as comprising two opposed ilanges, it is suilicient in certain cases to form the wheel 22 with but a single flange for engagement by the thread of the wormscrew. The wheel in either form may thus be very inexpensively formed by conventional molding procedures. The Wheel, as illustrated, is formed to rotate upon tubular part or cylinder 12e as a support, the rotation being induced in either direction by rotation of the Wormscrew in a corresponding direction.

Rotation of Wheel 22 is directly transferred or translated to a rotatable contact device whose function is to provide electrical interconnection between any selected portion of a contact area of a resistance element, and a conductive collector ring. The contact device 24 (FIG- URES 4, 14 and l5) is, for the illustrated exemplary form of the potentiometer, formed by a shearing and stamping operation, from a sheet of resilient conductive material such as one of the commercially-available contact alloys. The preferred contact device, as illustrated, is formed as an integral or single-piece element or part, and has a central opening or aperture 24a of a size to permit closely controlled rotation upon and about cylinder 12C. The contact device, herein termed the contact in the interest of brevity, is provided with a notch 24n in which is received a driving nub or key 22k that is attached to or formed integrally with the body of wheel 22 (FIGURES 8 and 9). As is indicated in FIGURE 3, the opposed horns or edges of the contact at opposite sides of notch 24u are tightly received in respective slots (such as 222 FIGURE 9) formed by respective overhangs or eaves such as 22e provided as integral parts of the key 22k. The contact is thus readily attached to wheel 22 before the wheel is mounted on cylinder 12a; and when the subassembly comprising the wheel and contact is mounted on the cylinder the contact is constrained to rotate with the wheel. The extent of rotation or angular traverse of the wheel 22 (and consequently also of the contact device 24) is limited by a stop or abutment 12s (FIGURE 3) that is provided in cover l2 preferably as an integral part of the cover, and which abutment is disposed in the path of stop means which comprise one or more extensions` or stops 22s (FIGURE 8) each formed as a radial protuberance extending outwardly in the general plane of one of the anges of the wheel 22. The stop means thus provided on the wheel 22, and the abutment means 12s provided in the cover I2, are so dimensioned that the contact point next to be described may not be drivenbeyond either end of the resistance element with which it cooperates. Thus those dimensions are related to the angular extent or length of the resistive part of the resistance element. The contact device 24 (FIGURES 14 and l5) is sheared along an arcuate zone or line 24z, to provide a fiat base 24b of 360 extent for supporting contact, or bearing, on wheel 22 and for proper rotational cooperation with the cylinder I2C, and to provide a divergent outwardly extending resilient limb 24s preferably of arcuate configuration integral at its ends with the base 24b. As is illustrated in FIGURE l5, the limb 24s is deformed adjacent its junctures with the base 24h, so as to diverge or extend away from the plane of base 24h, whereby to permit the limb to yield and to exert a force effective to maintain the contact point in effective electrical communication with the resistance element. The contact point, 24C, is provided on a radial extension of limb 24s, either as a pellet of precious metal fusion-united to the limb extension, or, as illustrated, as a protuberance formed by deformation or dimpling of the extension.

The cover l2 is provided adjacent its corners with a set of indentations or recesses such as those illustrated at 12m, 12in (FIGURE 3), which recesses are shaped and disposed to receive key-pins such as those illustrated at 14m, 14n (FIGURE 6) formed ras upstanding protuberances attached to or formed integral with, housing body 14. The key-pins are t-hus adapted to precisely position the cover on the body part 14. As is evident from examination olf FIGURE 5, the housing body part I4 is formed to provide a trough-like generally annular recess 141' that is partly encircled by `an upstanding wall 14W. 'Ilhe recess opens at one lside of the ybody part to provide space for placement of terminal means to be presently described, the wall being modified at that side by provision of outwardly extending channels 14k as indicated. The pant 14 also comprises a centrally disposed upstanding circular wall 14v the inside diameter of which is such as to provide .a close t around cylinder 12C of the cover part 12, as is indicated in FIGURE 7. The latter ligure makes evident the fact that after the two housing parts are brought into mating con-tact, Ithey may be adhesively secured and sealed together along the exterior juncture 10a and in the zone between cylinder 12C and wall 14v. `Disposed in recess 141', as is indicated in FIGURES 6 and 7, is an arcuate elongate resistance element 25 which in the illustrated exemplary embodiment of ya potentiometer is in the conliguration of a section of a toroid. The resistance element 25 comprises essentially a provided. As is indicated in FIGURE 13, the resistance element 25 has physically secured thereto and electrically .connectedV to Vrespective end portions of the resistive means, first and second termination tabs or strips 25t and 25u that are, in the case of the wire-typeresistive means shown, fusion-united with respective end portions of the wire -as by brazing yor welding. .The strips 2.5i and 25u are disposed below the resistance elementV in recess 14r, in complementary recesses 14e, idf formed in the floor of bodyfpart it (FIGURE );`and each strip hassecured thereto la respective terminal which in the illustrated embodiment is a respective one of wires 16, 16.

VBy the described means, excellent accurate electrical connections to the ends of the resistance element Iare provided.

' Disposed upon the upper substantially circular end face of wall rdv of body part 14, is an exposed conductive resilient collector ring 23 (FIGURE 11). The collector ring is deformed or bowed upwardly so las to present yielding uppermostcontact areas 2da, 28a each diametrically opposite the other, and to present two diametrioally opposite areas Zb, Ziib to rest upon wall 14V. Ring Z8 is provided with a terminating means 28t preferably in theform of an integral strip which is rformed `to depend from the ring and lie against the wall 14v in recess 1dr. Means 231i is electrically connectedk (as by brazing or welding) to a third terminal device, which device in the illustrated embodiment of a potentiometer is wire termin-al 15. The latter terminal is disposed in` the bottom of -fone of recesses 14k provided in the floor of part 14, las depicted in FlGURE.

' Subsequent to assembly of spacer 2.6, resistance element 12,5,V collector ring 28, and the respective terminal devices, in body' part 14, those parts `are secured in place 8 t properly disposed for cooperative action with the opposite member of a mounted potentiometer. As is evident, Where such a projection is provided and is not desired in a particular application of the potentiometer, the projection may be easily removed, as by scraping, abrasion or cutting. n

Agsv is evident, rotation of the wormscrew 18 (as by a tool applied to lhead 18h and rotated), irst induces rotation of wheel 22 and contact device 24 until engagement of the aforedescribed stop means'22s with abutment 12s oocurs,'after which any continued rotation of the wormscrew in the same direction-*merely results in slippage of the screwthread `of the wormscrew relative to the flange or flanges 'of wheel 22.. Thereafter, wormscrew rotation in the opposite direction causes immediate reverse rotation of the wheel and contact. Also it is evident that multiple stacking of po-tenti-ometer's of the same size orof different sizes lupon a single mounting `screw will not interfere in any way'with operation of either ofthe potentiometers thus mounted. Further, in those cases where pin llterminals extending downwardly through the body part are used in lieu of the wire terminals shown in the preferred embodiment (in which case multiple mounting may not be Vpractical and wherein in fact the potentiometer may be mounted -by its terminal pins) the advantage of a much larger than usual resistance element still accrues to the disclosed potentiometer. Thus it is evident that the aforey' mentioned objects of the invention are attained.

It further is evident that in the light of the present Y disclosure in detail of an exemplary potentiometer embodying the invention, changes and modifications will Voccur to those skilled in the art; and accordingly it isnot desired to limit the invention to the particular details oi the exemplary structure disclosed, `other than as they are specifically ldefined in the `appended claims.

by adhesive means such as insulative encapsulating or potting compound only a small portion of which is Vindicated, at 30 in FIGURE 7. 'The electrical connections and the element may then be tested as desired. With those parts thus assembled into la body sub-assembly, rand the previously described wormscrew, O-ring, wheel, oontact device, and retainer pin assemlbled in cover part v12,

adhesive is applied asnecessary and the twol housing parts Iare lbrought together and clamped yfor curing of the ladhesive. Additional compound or adhesive may be applied as necessary to insure complete closure ofthe open side of body par-t .14. As the 'two housing par-ts are brought together, cylinder 12 is entered into the central opening in body part 1.4', and 'one housing part rotated relative to the other (ifl necessary) to bring key 14m into line with Iits mating recess, and thepants are pressed together. In that action,y contact point 24e engages the exposed surface of the resistive means of the resistance element and points 28a of thering 28 engage the base 24h of the contact, the spring portions of those elements yieldingl and providing good contact. Y

While not essential, the housing parts may be provided with means for facilitating stacking and/or prevention of rotation upon the centrally disposed mounting screw. To that end, properly dis-posed protruding projections orpins such as 14x (FIGURES l and 4)y may be provided on We claim: t

' 1. A wormscrew-adjusted potentiometer comprising:

first means, comprising a box-like housing having first and sec-ondprincipal portions, said housing portions providing` opposite generally parallel faces, and structural means providing an unobstructed aperture through the housing from face to face thereof, said structural means being generally tubular in form and comprising a portion providing -a cylindrical bearing surface, said first and second principal portions being constructed and arranged to intert to provide in said housing an interior chamber, .and said structural means being rigidly held in place between said Ifaces, whereby said housing has a centrallylocated mounting hole therethrough for the reception of mounting means;

second means, comprising adjustable ypotentiornetric meansdisposed in saidfhousing around said structural means and comprising means mounted for rotation on said cylindrical bearing surface, and said second means comprising terminal means for said potentiometric means;

and third means, comprising wormscrew means supported by said'housing'and exposed for rotation by `means exterior of said housing, said wormscrew means being constructed and arranged with a Wormscrew thread in driving engagement with said second means for effecting adjustment thereof in response to rotation of said wormscrew means.

2.*A Wormscrew-adjusted potentiometer' as defined in claim `1, said second means cornprisingaV anged wheel rotatable on said cylindrical bearing surface and a movable contact rotatable by said wheel, said wheel having flange means engaging the worrnscrew thread fof said worrnscrew means tobe drivenk thereby.

`3. A wormscrew-adjusted potentiometer as defined in Y claim 2, said structural means comprising a tubular memofthe pin of a nextaadjacent potentiometer. As is evident,

a panel may similarly -be provided with a hole, or a pin,

ber integral with one of Ysaid rst and second portions, and said wheel being constructed and arranged to ro-A tate upon said tubularvportion.

V4. In a'wormscrew-adjusted potentiometer, first means 9 including potentiometric means including an arcuate resistance element, and means including a rotary contact therefor;

second means, comprising wormscrew means having a screw thread;

third means, comprising a toothless wheel having a circumferential radial flange, an annular substantially flat radial face of which flange presses against said screw thread to be Ifrictionally driven thereby incident to rotation of the w-ormscrew means, and means connecting said rotary contact to said wheel to be driven by the latter; and

fourth means, comprising housing means constructed and arranged to support said rst, Isecond and third means.

5. rPhe combin-ation dened by claim 4, said potentiometric means comprising a rotary contact device rotatable by said wheel' and further comprising an arcuate resistance element disposed coaxially with said contact device, and said third means comprising a tubular means providing a hole through said housing for reception of mounting means .and said tubular means providing bearing means for supporting saidtoothless flanged wheel and serving to restrain foreign material from entering said housing means.

6. A wormscrew-adjusted potentiometer comprising:

rst means, including a hollow box-like housing having upperV and lower faces presented respectively by first and second parts of said housing, said first part comprising a floorY portion and encircling marginal portions and a `centrallydisposed portion including an upstanding tubular portion, and said second part having a portion providing acentrally-located aperture closely encircling said centrally disposed portion of said first part, lwhereby to provide a mounting-hole for the potentiometer therethrough from face .to face;

second means, comprising an arcuate resistance element disposed in said housing and substantially encircling said tubular portion, and .first and second terminal means connected to respective ends of said resistance element and each extending through to the exterior of said housing;

third means, comprising a rotatable con-tact device constructed and arranged to rotate about said tubular portion and having first and second contact portions the first of which is disposed for wiping contact on said resistance element;

fourth means, comprising a conductive collector encircling said tubular portion and arranged to'be conductively wiped by said second contact portion, yand terminal meansconnected to said collector and extending to the exterior of said housing; and

fth means, including a rotary wheel disposed for rotation about said tubular portion and engaging said contact device for rotating the latter, and a wormscrew carried by said housing and exposed to the exterior thereof and engaging said rotary wheel for rotating the latter;

whereby said potentiometer or a plurality thereof may be mounted upon and secured in fixed position by -a single mounting device extended through the centrally-disposed hole therethrough, and whereby any such potentiometer may be adjusted by rotation of the wormscrew thereof.

7. A potentiometer according to claim 6, said first and second parts of said housing being of substantially square plan form, and said resistance element spanning from wall to wall inside said housing.

8. A potentiometer according to claim 6, said rotary wheel having a peripheral groove and being of pulleylike conformation with opposed rim flanges at least one of which is resilient, and a screw-thread portion of said wormscrew being disposed between said flanges for frictional driving engagement therewith.

9. A potentiometer according to claim 8, said rotary wheel comprising a peripheral protuberance on at least one of said flanges, and said housing comprising an inwardly extending abutment constructed and arranged to be engaged by said abutment to limit rotary movements of said rotary wheel.

10. A potentiometer according to claim 8, said rotary wheel being of resilient dielectric material and having an upstanding anchor on one of said flanges, and said rotatable contact device being of conductive material of generally circular plan form with said first contact point protruding from the periphery thereof and having portions forming a notch engaging said anchor to secure the said contact device to said rotary wheel.

11. A potentiometer according to claim 8, said wormscrew having a thread portion both ends of which engage the inner opposed faces of the rim flanges of said rotary wheel.

12. yIn la wormscrew-adjusted potentiometer, the combination comprising:

housing means, including first and second housing members of substantially square plan-form and having respective first and second substantially flat parallel faces and having portions defining a centrally disposed aperture therethrough perpendicular to said faces, said housing members being complementary and forming a tubular structure dening at least a part of said aperture and together providing an internal cavity;

wormscrew means including a wormscrew rotatably mounted in said housing means and having a screw portion exposed yat the interior of said cavity and having a driving end accessible from the exterior of said housing means;

rotary wheel means in said cavity and mounted for rotation about said tubular structure and engaging said screw portion for rotation incident to rotation of said wormscrew means;

conductive rotary contact means connected to said wheel means for rotation therewith, said contact means comprising inner and outer contact areas electrically interconnected;

resistance element means disposed in said cavity and substantially encircling said tubular structure and having an arcuate exposed area arranged to be wiped by said outer contact area incident to rotation of said rotary wheel means;

conductive collector means substantially encircling said tubular structure and disposed for wiping engagement with said inner contact area of said rotary contact means; and

electrical means, including terminal devices attached and connected to respective ends of said resistance element means, and a terminal device connected to said collector means, said terminal means extending from within said cavity to the exterior of said housing means.

13. The combination defined by claim 12, said rotary Wheel means being of flat bobbin-shape having outwardly directed peripheral flanges at least one of which is resilient, and said flanges clasping said wormscrew means for driving engagement therewith.

14. The combination defined by claim 13, said rotary wheel means having a peripheral protuberance yand said, housing having an abutment disposed for coaction with said protuberance to limit rotation of said wheel means when said wheel means is overdriven by said wormscrew means, said wormscrew slipping relative to said wheel means when overdriven with rotation of the said wheel means prevented by said abutment.

l5. The combination defined by claim 12, said first housing member having a centrally disposed .tubular portion providing said centrally-disposed aperture, and said second housing member having a centrally disposed tubular structure disposed in concentric relation with respect to the sajid tubular portiorg;andymeansadhesively vsecur- Y ing said housing members together.

16. The combination-defined by claim 12, said resisty ance element means being secured to said second housing member in said cavity, and said collector being in the form of a flat ring disposed on the end` of sai-d tubular structure `and substantially concentric with said resistance element. v

y17. For a potentiometer of the type comprising as functional components ,an arcuate elongate resistance element, rotatable contact means having a contact in wiping relationship with the resistance element, a screw-threaded shaft, and a rotary element rotatable by the screwthreaded shaft and Vsecured to said contact means for rotating the latter, improvements in housing and supporting means comprising first and second housing members, saidvrst member comprising a floor portion presenting a flat exterior face and encircling lupstanding wallvportions integral therewith and a centrally-disposed upstandq ing tubular portion perpendicular to said face and dis-y posed inwardly from said wall portions, and said second member having a portion pnoviding 'a flat surface encircling a centrally disposed aperture axially aligned with and closelyfreceiving said' tubular portion of said rst y member, 'and said .second member and said first member being disposed with said faces substantially parallel yand having interengaging portions at said wall portions whereby to providev a box-like housing having a centrallydisposed aperture therethrouglnand said, housing being constructed' and arranged to housesaid functional components, whereby said potentiometer caribe mounted and Vaffixed in spatialposition on a single rod-like mount.

18. Improvements according to claim 17, said housing members being of substantially square plan form.

19. Potentiometric means comprising: first means, including housing means presenting first and second opposite Afaces at least one of which is Y flat, saidhousingj means Vincluding means providingv a centrally-located. hol-e therethrough from face to faceV thereof for reception of a mounting screw or the like, said last-namedjmeans comprising generally tubular means around said hole adapted to bear compressive stress appliedto said housing means Vin mounting the latter; K g second means, including rotary means including potentiometer Contact means and ,Wheel means, disposedk for rotation on said tubular means in said housing means; j j f N third means, including resistance-element means in said housing means, disposed around said tubular means and spaced radially outwardly therefrom and constructed and arranged to be brushed by said contact means; and s fourth means, comprising wormscrew means including a screwthread exposed in said housing in driving engagement with said rotary means,

- whereby said potentiometric means ymay be mounted upon a single mounting element and may be adjusted by yrotati-on of -said kWormscrew means.

References Cited in the :file of this patent i UNITED STATES PATENTS 'Austria Jani 10.1962 

4. IN A WORMSCREW-ADJUSTED POTENTIOMETER, FIRST MEANS INCLUDING POTENTIOMETRIC MEANS INCLUDING AN ARCUATE RESISTANCE ELEMENT, AND MEANS INCLUDING A ROTARY CONTACT THEREFOR; SECOND MEANS, COMPRISING WORMSCREW MEANS HAVING A SCREW THREAD; THIRD MEANS, COMPRISING A TOOTHLESS WHEEL HAVING A CIRCUMFERENTIAL RADIAL FLANGE, AN ANNULAR SUBSTANTIALLY FLAT RADIAL FACE OF WHICH FLANGE PRESSES AGAINST SAID 